/*
 *                               POK header
 *
 * The following file is a part of the POK project. Any modification should
 * be made according to the POK licence. You CANNOT use this file or a part
 * of a file for your own project.
 *
 * For more information on the POK licence, please see our LICENCE FILE
 *
 * Please follow the coding guidelines described in doc/CODING_GUIDELINES
 *
 *                                      Copyright (c) 2007-2021 POK team
 */

/* e_atan2f.c -- float version of e_atan2.c.
 * Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com.
 */

/*
 * ====================================================
 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
 *
 * Developed at SunPro, a Sun Microsystems, Inc. business.
 * Permission to use, copy, modify, and distribute this
 * software is freely granted, provided that this notice
 * is preserved.
 * ====================================================
 */

#ifdef POK_NEEDS_LIBMATH
#include "math_private.h"
#include <libm.h>

static const float tiny = 1.0e-30, zero = 0.0,
                   pi_o_4 = 7.8539818525e-01, /* 0x3f490fdb */
    pi_o_2 = 1.5707963705e+00,                /* 0x3fc90fdb */
    pi = 3.1415925026e+00,                    /* 0x40490fda */
    pi_lo = 1.5099578832e-07;                 /* 0x34222168 */

float __ieee754_atan2f(float y, float x) {
  float z;
  int32_t k, m, hx, hy, ix, iy;

  GET_FLOAT_WORD(hx, x);
  ix = hx & 0x7fffffff;
  GET_FLOAT_WORD(hy, y);
  iy = hy & 0x7fffffff;
  if ((ix > 0x7f800000) || (iy > 0x7f800000)) /* x or y is NaN */
    return x + y;
  if (hx == 0x3f800000)
    return atanf(y);                       /* x=1.0 */
  m = ((hy >> 31) & 1) | ((hx >> 30) & 2); /* 2*sign(x)+sign(y) */

  /* when y = 0 */
  if (iy == 0) {
    switch (m) {
    case 0:
    case 1:
      return y; /* atan(+-0,+anything)=+-0 */
    case 2:
      return pi + tiny; /* atan(+0,-anything) = pi */
    case 3:
      return -pi - tiny; /* atan(-0,-anything) =-pi */
    }
  }
  /* when x = 0 */
  if (ix == 0)
    return (hy < 0) ? -pi_o_2 - tiny : pi_o_2 + tiny;

  /* when x is INF */
  if (ix == 0x7f800000) {
    if (iy == 0x7f800000) {
      switch (m) {
      case 0:
        return pi_o_4 + tiny; /* atan(+INF,+INF) */
      case 1:
        return -pi_o_4 - tiny; /* atan(-INF,+INF) */
      case 2:
        return (float)3.0 * pi_o_4 + tiny; /*atan(+INF,-INF)*/
      case 3:
        return (float)-3.0 * pi_o_4 - tiny; /*atan(-INF,-INF)*/
      }
    } else {
      switch (m) {
      case 0:
        return zero; /* atan(+...,+INF) */
      case 1:
        return -zero; /* atan(-...,+INF) */
      case 2:
        return pi + tiny; /* atan(+...,-INF) */
      case 3:
        return -pi - tiny; /* atan(-...,-INF) */
      }
    }
  }
  /* when y is INF */
  if (iy == 0x7f800000)
    return (hy < 0) ? -pi_o_2 - tiny : pi_o_2 + tiny;

  /* compute y/x */
  k = (iy - ix) >> 23;
  if (k > 60)
    z = pi_o_2 + (float)0.5 * pi_lo; /* |y/x| >  2**60 */
  else if (hx < 0 && k < -60)
    z = 0.0; /* |y|/x < -2**60 */
  else
    z = atanf(fabsf(y / x)); /* safe to do y/x */
  switch (m) {
  case 0:
    return z; /* atan(+,+) */
  case 1: {
    uint32_t zh;
    GET_FLOAT_WORD(zh, z);
    SET_FLOAT_WORD(z, zh ^ 0x80000000);
  }
    return z; /* atan(-,+) */
  case 2:
    return pi - (z - pi_lo); /* atan(+,-) */
  default:                   /* case 3 */
    return (z - pi_lo) - pi; /* atan(-,-) */
  }
}
#endif
